In technical terms, a is an Android package that includes a digital signature. This signature serves two primary purposes:
For the user, seeking a signed version is a way to verify that the app is "official" or at least structurally sound, even if it is being sourced from a third-party repository rather than the Google Play Store. The Risks of Sideloading Download Banner Maker signed apk
Hidden scripts that scrape personal information. In technical terms, a is an Android package